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There are countless things we must still learn about the millions of creatures on earth -- including where the heck they all live

The key to biodiversity is geography. Charles Darwin understood as much in 1857 as he was puzzling over the flora and fauna of the Galápagos Islands on his way to writing On the Origin of Species. "One of the subjects on which I have been experimentising & which cost me much trouble, is the means of distribution of all organic beings found on oceanic islands," he wrote to a colleague. Why, he wondered, are certain animals and plants where they are? What makes a place biologically unique?

Ecology has come a long way since then. Through online databases like the Encyclopedia of Life, scientists worldwide can share and parse data about the traits and habits of millions of species. Yet they still know surprisingly little about where, exactly, things can be found. Look up your favorite species in a field guide; you'll see a Rorschach-style blot indicating its range. These "blob maps," as Robert Guralnick, an evolutionary biologist at the University of Colorado at Boulder, calls them, are accurate to within maybe 60 miles. But that's no longer good enough to meet the environment's challenges.

"They're lovely -- they inform our knowledge of where things are," Guralnick says of these maps. "However, they're not so good if you want to throw a dart and ask, ‘Am I going to find such-and-such a bird at this spot in Borneo?' The resolution is too coarse."

Now Guralnick and Walter Jetz, an ecologist at Yale, have joined forces to give us something better. The online database they've created, the Map of Life, aspires to be the most precise range map for every species in the world. It culls distribution data from a wide field of sources, including the Global Biodiversity Information Facility, the World Wildlife Fund, and various national park surveys. At the moment, in demo form, the Map of Life offers range data on 25,000 terrestrial vertebrates and North American fish; the ultimate aim is to describe "the when and where" of millions of species, Jetz says. "It will give us a window on the actors and their interactions," Guralnick adds, "and strong assessments of their continued likelihood of existence."

This is not your grandmother's blob map. The distribution data are nearly infinitely searchable and can be made almost instantly visible. A user can ask a basic question like "Where in the world is the yellow wattlebird?" and get an answer in unprecedented detail. One can map the whereabouts of dozens of species simultaneously, or pick a spot large or small, in Borneo, or British Columbia, or Chicago, and ask: "What are all the species that are found nearby?"

Employed in this manner, the Map of Life could come to serve as a powerful tool for revealing -- and conserving -- biodiversity. One could pinpoint a proposed dam site, say, in order to analyze which local species might be threatened or endangered -- and assess just how species-rich that particular area is compared with others nearby. Or one could determine where in a given state or country the highest concentrations of threatened species lie, with an eye toward identifying the most promising location for a nature preserve. In Jetz's words, "We can have a quantitative basis for conservation prioritization."

The map -- which is adding taxa and functionalities all the time -- is viewable at its own URL (mappinglife.org), but may soon also be available on sites like the Encyclopedia of Life. As the map develops, it will integrate new information about temperature, rainfall, and other factors to generate ecological impact studies of a sort -- again, not simply for one species, but for dozens at once, at any location.

That, says Guralnick, is where it has the potential to be the most powerful. Instead of studying the interactions of species as if observing them from outer space, ecologists will be able to zoom in and study all kinds of interactions "at a scale that matters to the organisms themselves." As the database fills in, it will reveal how the distributions of species are changing over time; biologists might then get a clearer view of how, say, the range of a certain bird species is altered by changes in forest coverage, or by rising temperatures. Jetz says it will allow scientists "to be objective in our understanding of biodiversity distribution and the mechanics behind it, as well as our projection of potential threats."

All told, the map will paint a portrait -- interactive and constantly updated -- of biodiversity in motion, for better and for worse. "It gives you a sense of dynamism," Guralnick says. "Species have ranges; they shift and collapse or grow as the world itself changes. New communities assemble or disassemble as the rate of change ramps up. It's a rapidly changing environment out there."

Indeed it is, ever more so. For ecologists, as much as for the species they study, it's a struggle just to keep up.

Alan Burdick is a senior editor at The New Yorker and author of "Out of Eden: An Odyssey of Ecological Invasion," which was a National Book Award finalist. He blogs at www.aburdick.com and tweets at @alanburdick.

OnEarth is published by the Natural Resources Defense Council. The opinions expressed by its editors and writers are their own and do not necessarily reflect the policies or positions of NRDC. Learn more.